When Miami police officer Nathaniel Dauphin stepped into federal court to face an extortion charge Wednesday, he became the first of several officers expected to be swept up in a broad anti-corruption dragnet of the city’s beleaguered police department.

Dauphin, 41, allegedly helped organize a protection racket for a sports-betting ring working out of a Liberty City barber shop. He pleaded not guilty to a single charge of extortion conspiracy, alleging that he “protected and facilitated illegal activity — gambling — in exchange for receipts of cash payments.”

Dauphin, a police officer since 1996, was allegedly paid $5,000, according to the charge. The government filed papers to seize that money from him.

Miami Mayor Tomás Regalado portrayed the arrest as part of an ongoing cleansing of the police department, whose internal affairs investigators worked the case with the FBI.

“I really believe that this is good,” he said. “It tells the citizens of Miami that the force is looking at itself, and it tells the officers that they are under scrutiny.”

On Friday, another Miami officer, Sgt. Raul Iglesias, was found guilty by a federal jury on unrelated charges of stealing money and drugs from street dealers and lying to federal agents. His sentencing is set for March.

In Dauphin’s case, the fact that he was charged by “criminal information’’ indicates that he has been cooperating with federal authorities and is expected to eventually change his plea to guilty. The single charge carries a maximum sentence of 20 years, but he is likely to receive more-lenient punishment for his assistance.

Dauphin was granted a $100,000 bond under an agreement between the U.S. attorney’s office and his defense attorney, David Howard, who declined comment.

Dauphin, who was allowed to surrender to authorities and was released Wednesday afternoon, is among at least 10 Miami police officers expected to soon face federal criminal charges or internal discipline related to the protection scheme and other criminal activity, The Miami Herald has learned.

Seven of the officers under scrutiny have already resigned or been relieved of duty in recent weeks, according to sources close to the probe.

“Anytime a police officer is arrested, it’s a sad day for our police department,” said Fraternal Order of Police President Javier Ortiz, whose union is not representing Dauphin.

Police Department spokesman Sgt. Freddie Cruz declined comment.

The FBI, which has been working with Miami internal affairs investigators since the gambling operation was shut down in March 2012, is expected to make more arrests before the end of the month. Internal affairs’ investigators attended Dauphin’s first appearance in federal court Wednesday.

The targeted officers, who worked in the Model City substation, are suspected of providing off-the-books protection and frequenting the Player’s Choice Barber Shop, 6301 NW Sixth Ave., so often that one gambler told county police he thought the place was being run by the Miami Police Department, state court records show.

Earlier this month, four officers including Dauphin were relieved of duty, according to the department. The others were Malinsky Bazile, 27, Vital Frederick, 26, and Angel Mercado, 29, who are suspected of other criminal activity unrelated to the alleged protection racket. All continue to receive pay while the investigation continues.

Last month, The Herald reported that 31-year-old officer Lashunda Hodge was relieved of duty with pay as part of the protection-detail probe.

Another likely target of the investigation, Officer Harold James, resigned in late November. At least three other Miami officers are facing scrutiny in connection with the protection scheme: Hodge’s roommate, Kenya Crocker, 39; Dauphin’s girlfriend, Carol Vargas, 39, and Darryl Bryant, 51, according to sources familiar with the case.

The FBI investigation has focused largely on Hodge and Dauphin. Investigators believe Hodge was the original ringleader of the protection scheme, and Dauphin later managed the operation, sources said. Hodge’s lawyer has denied that she set up the protection.

Sources say the officers received thousands of dollars in unsanctioned payments to provide off-duty protection to the barber shop from mid-2010 through last March. The shop has since closed.